I believe Bracket Highlighters default key binding is "ctrl+shift+b, ctrl+shift+[" (replace ctrl with super if on mac). It is a key binding sequence. You can check the BracketHighlighter keymap file to confirm. This shortcut actually conflicts with a build system shortcut that uses "ctrl+shift+b", so this shortcut will be removed in the next version of BracketHighlighter and will require the user to define the shortcut themselves, but currently it should be as described above.